Piston



Sept. 1946. R. R. TEETOR 2,407,192

' PISTON Filed Ma 25, 1944 r INVENTOR.

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Patented Sept. 3, 1946 The Perfect Circle Company, Hagerstown, Ind., a corporation of Indiana Application May 25, 1944, Serial No. 537,252

This invention relates to pistons adapted more particularly for use in internal combustion engines. y

The main object of this invention is to provide a light-weight, simple and inexpensive piston which will afford, throughout the operating temperatures and speedranges of the engine, the most efficient clearance between the piston skirt and the cylinder wall.

More particularly, I provide a piston, having a slotted skirt formed of aluminum alloy or similar light-weight material, with one or more bands of wire wound spirally andtightly around the skirt of the piston to reduce the unconfined diameter of the piston, the'wire being formed of a-metal having a coefiicient of expansion lower than that of the skirt and approximating that of the metal of the engine cylinder. The ends of the wire are securedor anchored to the skirt. My invention eliminates piston skirt collapse, piston slap, excessive wear and scufling, and also provides better oil control.

Other objects and advantages will become apparent as this description progresses and by reference to the drawing, wherein- Figure 1 is an elevational view of one form of tpiston, constructed in accordance with my invenion;

Fig. 2 is a similar view of the piston, taken at 90 degrees to Fig. 1;

Fig. 3 is an enlarged detail vertical section, taken on the line 3-3 of Fig. 2; and

Fig. 4 is an enlarged detail horizontal section taken on the line 4-4 of Fig. 3.

The piston is made of an aluminum alloy or a similar metal which is light in weight and has a higher coefficient of expansion than the cast iron or steel wall of the engine cylinder in which it is to operate. I have illustrated the piston as having a head 5 and an integral skirt 6 which is provided with a T-shaped slot 1 consisting of a horizontal slot la adjacent the head and a vertical or longitudinal slot lb extending from the slot la to the lower edge of the skirt. The vertical slot 1b is midway between the piston pin bosses, the openings through which are illustrated at 8 in Figs. 1 and 2. The piston, as far as has been described, is of a well-know type but I do not intend to limit my invention thereto, as my invention is adapted for use in any type of piston having a skirt with a longitudinal slot.

Formed in the outer surface of the skirt are grooves, preferably two, one 9 near the top of the skirt and the other l near the bottom of the skirt. Each groove is provided with a spiral 4 Claims. (Cl. 309-13) thread l2. Tightly wound i each spiral thread: is a wire I3. Part of the wire in .the lower groove is shown broken away in Fig. I. v

In applying each wire band IS to its roove; one end of thefwire is thrustthrough a round hole 15 (Fig. 3) in the piston skirt atone end of the spiral groove, and the projecting extremity of p the wire within the ski'rtis then bent at right angles, as shown in Fig. 3, to firmly anchor'the end of the wire. If desired, the extremityof the wire may first be bent "at rightangles and "then the other end of the wire may be threaded through the hole Hi from the inside of the skirt and the wire drawn through the hole. The wire is then wound under considerable tangential tension or pull in thespiralthread-,"the tension being such; that the force exerted "reduces the, unconfined diameter of the skirt to its final desiredeilfe'etive diameter. It will be understood that the diameter may be so reduced because of the vertical slot 1b, which is partially closed. By unconfined diameter, I mean the diameter of the skirt at around room temperatures, after the skirt is slotted and finished but before the wire bands are applied.

In order to anchor the other end of the wire, I provide the skirt at the other end of the spiral thread with a horizontal slot IS. The wire near the end of the last turn is temporarily clamped against movement and then the free terminal of the wire is pushed into the slot, as indicated by the dotted lines I! in Fig. 3, and then while a pull, as with pliers, is exerted on the terminal, it is bent into a hook around the adjacent end of the slot, as shown in Fig. 3. The clamping means on the wire is then removed, the end of the wire being firmly fastened to the skirt.

Each wire is formed of a metal having a coeflicient of expansion lower than that of the metal of the skirt and approximating the coeflicient of iron or steel. The wire may be formed of carbon steel and may be similar to that used in musical instruments. I prefer to use a wire having a diameter in the neighborhood of .050 of an inch.

It will be observed that the outer portions of the turns of each band extend slightly, that is, around .005 of an inch, beyond the outer cylindrical surface of the skirt, though, in the broader aspects of my invention, the turns may be flush with this surface or even inset with relation to it.

It is well known that pistons formed of aluminum alloy and the like have a much higher coefficient of expansion than cast iron or steel, of which the cylinder, in which it operates, is formed, and that the slotted skirt tends to collapse, with resultant piston slap, when the engine is cold, and

if rigid enough to resist collapse, the skirt expands and exerts pressure against the cylinder wall, when hot, with resultant excessive wear and scuffing. I have found that with my invention, the skirt, having its unconfined diameter reduced by wire bands, which constantly compress the skirt, the latter may be given suflicient rigidity to prevent collapse when cold, while, at the same time, the wire bands expand and permit the skirt toexpand when hot, in substantially the same ratio as the expansion of the cylinder wall, so:

that the most effective clearance is maintained and undue wear and scufling are overcome.

With the outer portions of the. turns of the wire bands projecting slightly beyond the outer surface excellent bearings for the skirt against the cylinder wall.

I claim:

1. In a piston for internal combustion engines,

a piston skirt provided with a longitudinal slot and formed of metal. having a coefficient of expansion higher than that of cast iron or steel, a wire formed of metal having. a lower coeflicientof expansion than that of the skirt and tightly wound in a series of turns around the slotted portion of the skirt andv compressing the skirt to reduce its unconfined. diameter to its final efiective diameter, and means for fasteningv the ends of the wire to the skirt.

2. In a piston for use in a cylinder of an internal combustion. engine, a piston skirt provided with a longitudinal. slot and a circumferential groove and formed of metal having a coefficient of expansion higher than that of cast iron or steel,

a wire formed of metal having a lower coeflicient of expansion than. that of the skirt and tightly wound in said groove in a seriesof turns around l5 of the piston, the bands, in my judgment, form the slotted portion of the skirt and compressing the skirt to reduce its unconfined diameter to its final eflective diameter, with the outer portions of the turns of wire projecting beyond the outer surface of the skirt to provide a bearing adapted to engage the wall of the cylinder, and means for fastening the ends of the wire to the skirt.

3. In a piston for use in a cylinder of an internal combustion engine, a piston skirt provided with a longitudinal slot and a circumferential groove with a spiral thread and formed of metal having a coefficient of expansion higher than that of cast iron or steel, a wire formed of metal having alower coeflicient of expansion than that of the skirt and. tightly wound in the spiral thread of said groovev in a series of turns around the slotted portion of the skirt and compressing the skirt to reduce its unconfined diameter to its final efiective diameter, and means for fastening the ends of the wire to the skirt.

4. In a piston for use in a cylinder of an internal combustion engine, a piston skirt provided with a longitudinal slot and a circumferential groove with a spiral thread and formed of metal having a coeflicient of expansion higher than that of cast iron or steel, a wire formed of metal having a lower coefficient of expansion than that of the skirt and tightly Wound in the spiral thread of said groove in a series of turns around the slotted portion of the skirt and compressing the skirt to reduce its unconfined diameter to its final eifective diameter, with the outer portions of the turns of wire projecting beyond the outer surface of the skirt to provide. a bearing adapted to engage the wall of the-cylinder, and means for fastening the ends of the wire to the skirt.

RALPH R. TEETOR. 

